Yes that's a good advice some people often choose to hodl but when they look at the market after 3 days or just 1 week they are panicking and sell their holdings, I really think you should know to yourself what kind of trader you are and where you are comfortable at before investing to either trading or investment.
If they decide to sell their holdings and panic to see the price it goes down, that will be the mistake because they will not make anything except losing their money value.
If they can still hold and buy back for more when the price is down, they will see their profit will come to them.
But that will only be for the potential coins because not all coins can profit and they need to search by themselves.
Investing needs calculation of the money and how long the time to hold the investment so we know when we can sell the investment and leave the market temporary.